MDSC 1102 PBL 1

By Arvind Seecharan (Future Doctor Extraordinaire)

Learning Objective 1

• Describe the gross anatomy of the heart

The Heart • The heart is a hollow, fibromuscular, thick-

walled organ located in the middle mediastinum of the thorax.

• It is also a double, self-adjusting muscular pump, which receives oxygenated blood from the pulmonary circulation and propels blood through the systemic circulation to all the tissues of the body.

The Heart • A little bit larger than the closed fist of the

owner, the heart has an average weight range of 280 –340gm ( ) and 230 – 280gm ( ).♂ ♀

• It is conical in shape and possesses a base, three surfaces, six borders and an apex

External View

Anterior View of the Heart

Anterior Cross-Section of the Heart

Posterior Surface of the Heart

Surfaces of the Heart

Sternocostal (Anterior) Surface• This surface lies directly behind the sternum and

the 3rd to 6th right and left costal cartilages. It is formed by the two ventricles (2/3 right and 1/3 left). It contains the anterior part of the coronary sulcus and the anterior interventricular sulcus

Surfaces of the HeartSternocostal (Anterior) Surface

Pulmonary (Left) Surface:• This is the surface in contact with the cadiac notch of the

left lung. It is formed by the left ventricle.

Apex • The apex of the heart is formed by the left ventricle and

directed inferolaterally to the left. It is located in the left 5th intercostal, 9cm from the midline, slightly medial to the midclavicular line and below the left nipple.

Surfaces of the Heart

Diaphragmatic (Inferior) Surface: • This surface is directed inferiorly and related to the

central tendon of the diaphragm. It accommodates the posterior interventricular sulcus and is pierced by the inferior vena cava. It is also formed by the two ventricles (1/3 right and 2/3 left).

Surfaces of the Heart

Base (Vertebral or Posterior surface):• This is directed posterosuperiorly and to the

right, and lies opposite T5-T8 or T6-T9. It is formed by the two atria. This surface also contains the posterior part of the coronary sulcus (Atrioventricular sulcus).

Surfaces of the Heart

Base (Vertebral or Posterior surface):• The ascending aorta and the pulmonary trunk

emerge from the heart from the upper border of this surface while the superior vena cava enters the heart through the same border. This surface also receives the four pulmonary veins and the inferior vena cava.

Surface Anatomy of the Heart

• This is the surface projection of the four borders of the sternocostal surface of the heart to the anterior chest wall. Reference to the letters in the diagram above:

• AB: This represents the upper border. A is located at the upper border of the right 3rd costal cartilage, about 2cm from the midline. B is located at the lower border of the left 2nd costal cartilage 2 to 3 cm from the midline.

Surface anatomy of the Heart

• BC: This represents the left border of the heart. C is located at the left 5th intercostals space about 9cm from the midline.

• CD: This represents the inferior border of the heart. D is located behind the right 6th costal cartilage about 2cm from the midline.

• DA: This represents the right border of the heart.

Surface anatomy of the Heart

nd intercostal space

Surface anatomy of the HeartSURFACE ANATOMY OF THE HEART VALVES • This is the surface projection of the orifices

between the atria and the ventricles as well as those between the ventricles and the roots of the great vessels (Ascending aorta and the Pulmonary trunk). With the aid of the diagram above

• The valves are aligned in an oblique plane, which

lies parallel to and on the left aspect of the anterior part of the coronary sulcus.

Surface anatomy of the Heart• P is the pulmonary orifice. It is located behind the

sternal end of the left 3rd costal cartilage. This valve is auscultated at the sternal end of the 2nd left intercostal space.

• A is the aortic orifice. It is located at the sternal edge of the left 3rd intercostal space. This valve is auscultated at the sternal end of the 2nd right intercostal space.

Surface anatomy of the Heart• M is the mitral (Left atrioventricular or bicuspid)

orifice. It is located behind the left half of the sternum at the level of the 4th costal cartilage. This valve is auscultated in the left 5th intercostal space 9cm from the midline. This is also called the apex beat of the heart.

• T is the Tricuspid (Right atrioventricular) orifice. It is located behind the middle of the sternum at the level of the 4th intercostal space. This valve is auscultated at the midpoint of the sternum at the level of the 5th intercostal space

Structure of the Heart – Coverings• Fibrous pericardium• Serous pericardium

– Parietal pericardium– Visceral pericardium

Sulci of the heart

• Coronary sulcus– Atrioventricular sulcus

• Circumvents the heart

• Interventricular sulcusThe ventricles of the heart are separated by two

grooves, the1. Anterior interventricular sulcus2. Posterior interventricular sulcus

Coronary sulcus

• The atria of the heart are separated from the ventricles by the coronary sulcus.

• It contains the trunks of the nutrient vessels of the heart, and is deficient in front, where it is crossed by the root of the pulmonary artery

Anterior Interventricular Sulcus

• Is situated on the sternocostal surface of the heart, close to its left margin.

The posterior interventricular sulcus

• From this view, the coronary sulcus can be seen to separate the left and right atria from the left and right ventricles.

• The posterior interventricular sulcus separates the right ventricle from the left ventricle and if followed inferiorly, it can be seen to be almost continuous with the anterior interventricular sulcus.

Heart Features• Chambers

–Right atrium–Right ventricle–Left atrium–Left ventricle

• Valves– Leaflet valves

• Tricuspid• Bicuspid (mitral)

– Cusped (semilunar) valves• Aortic• Pulmonic

Right atrium• Auricle (ear)• Pectinate muscles (rough)• Sinus venarum (smooth)

– Crista terminalis• Division between rough to smooth

• Openings (ostia)– SVC/IVC/Coronary sinus

• Fossa ovalis– Foramen ovale in fetus– Limbus

Right atrium “valves”

• Superior vena cava– No valve

• Inferior vena cava– Eustachian valve

• Incompetent in adult, directs IVC blood though Foramen ovale in fetus

• Coronary Sinus– Thebesian valve

• Prevents backflow into coronary sinus during atrial systole

RA

Left atrium

• Ostia of 4 pulmonary veins– 2 superior– 2 inferior

• Auricle

LA

Right ventricle

• Most anterior aspect of heart• Tricuspid valve (RA-RV)

– Anterior/Posterior/Septal cusps (leafs)

• Papillary muscles– Connected to cusps via Chordae tendinae– Contract to prevent Tricuspid valve regurgitation– Named same as cusps

• Trabeculae carnae• Moderator band

RV

Left ventricle

• Trabeculae carnae• Bicuspid (mitral) valve

– Anterior/Posterior cusps• Papillary muscles

– Chordae tendinae• Usually a greater number than the right, due to the

increased pressures and strength necessary to prevent regurgutation

LV

Pulmonic valve

• From RV to pulmonary trunk• Lies just anterior to aortic valve• 3 semilunar cusps

– Anterior– Right– Left

A

P

Aortic valve• Posterior to pulmonic valve• Just superior lies the Sinus of Valsalva

– Helps to dampen aortic outflow and prevent cusps from adhering to walls of aorta

• 3 cusps– Posterior (non-coronary) cusp– Right– Left

• Just superior to right and left cusps in the Sinus of Valsalva are the openings of the right and left coronary arteries, respectively

Heart Valves• Tricuspid valve

– RA – RV • Bicuspid valve

– LA – LV– aka “Mitral valve”

• Aortic valve– LV – aorta

• Pulmonic valve– RV – pulmonary trunk

Right coronary blood supply

• Right coronary artery– Originates from ostia in right aortic sinus

• Superior to right aortic cusp

– Travels in right coronary (AV) sulcus– Branches

• Right marginal arteries (acute marginal aa)• Posterior interventricular a. (in post. IV sulcus)• Sinoatrial nodal a.• Atrioventricular nodal a.

Left coronary blood supply

• Left coronary artery– Originates from ostia in left aortic sinus

• Superior to left aortic cusp

– Branches• Left anterior descending (LAD) or anterior

interventricular a. (lies in anterior IV sulcus)– Septal branches.– Diagonal branches

• Left marginal aa. (Obtuse marginal aa.)• Left circumflex a.

Dominance

• Defined by branch that gives rise to posterior interventricular a.– Right (80%)

• From right coronary a.

– Left (15%)• From left circumflex a.

– Co-dominance (5%)

Venous drainage of the heart• Coronary sinus

– Lies in coronary (AV) sulcus on posterior– Opens directly to right atrium– All venous drainage of the heart eventually flows here

• Great cardiac vein– With LAD in anterior IV sulcus

• Left marginal vein

• Middle cardiac vein– With posterior interventricular a.

• Small cardiac vein– With right coronary a.

• Right marginal vein

• Oblique vein (LA)• Posterior vein of the left ventricle

Learning Objective 2

• Describe the innervation and the conducting system of the heart.

Innervation of the Heart

• The strength and frequency of the heart beat is controlled by the autonomic nervous system (parasympathetic and sympathetic parts)

• The sympathetic fibers arise from segments T2-T4 of the spinal cord and are distributed through the middle cervical and cervico-thoracic ganglia and the first four ganglia of the thoracic sympathetic chain. The sympathetic fibers pass into the cardiac plexus and from there to the SA node and the cardiac muscle.

Innervation of the Heart

• The effect of the sympathetic nerves at the SA node is an increase in heart rate. The effect on the muscle is an increase in rise of pressure within the ventricle, thus increasing stroke volume.

• The vagus provides the parasympathetic control to the heart. The effect of the vagus at the SA node is the opposite of the sympathetic nerves, it decreases the heart rate. It also decreases the excitability of the junctional tissue around the AV node and this results in slower transmission. Strong vagal stimulation here may produce AV block.

Innervation of the Heart

• The heart also has an internal nervous system made up of the SA (sinuatrial node) and the AV (atrioventricular) node. The AV bundle (His) leaves the AV node near the lower part of the interatrial septum and splits over the upper part of the interventricular septum into a left bundle branch (LBB) and a right bundle branch (RBB). The cardiac muscle is then supplied by branches of the two bundles.

SVC - superior vena cavaIVC - inferior vena cavaAO - aortaRA - right atriumRV - right ventricleLV - left ventricleCS - opening of the coronary sinus

Conducting system

Learning Objective 3

• Describe normal heart sounds.

Normal Heart Sounds

• Normal heart sounds are produced by closure of the valves of the heart. Flow through the valves will affect the sound the valve makes. Thus, in situations of increased flow (exercise for example) the intensity of the heart sounds will be increased. In situations of low flow (shock for example) the intensity of the heart sounds will be decreased.

Normal Heart Sounds

• S1: The S1 sound is normally the first heart sound heard. See the diagram below for the location of S1 during the cardiac cycle. The S1 is best heard in the mitral area, and corresponds to closure of the mitral and tricuspid (AV) valves. A normal S1 is low-pitched and of longer duration than S2.

Normal Heart Sounds

• S2: The S2 sound is normally the second sound heard. The S2 is best heard over the aortic area, and corresponds to closure of the pulmonic and aortic valves. A normal S2 is higher-pitched and of shorter duration than S1. The flow from the ventricles is more forceful than the flow from the atria. Therefore, S2 will normally be the louder sound

Normal Heart Sounds

• http://www.nlm.nih.gov/medlineplus/ency/anatomyvideos/000067.htm

• http://www.youtube.com/watch?v=39n4XWv7flQ&feature=related

• http://www.youtube.com/watch?v=Ge12P7u0aQo

Learning Objective 4

• Explain the physiological basis of heart murmurs.

What are Murmurs

• Murmurs or Bruits are the terms used to denote any abnormal sounds heard at any part of the cardiovascular system

• The two terms can be used interchangeably, although the term murmur is more commonly associated with abnormal sounds of the heart

Brief Overview of Blood Flow• In a person with regular blood flow, their

blood flow is described as Laminar and Non-turbulent.

• Blood flow is only non-turbulent up to a critical velocity. Above that velocity, it is described as Turbulent.

• Laminar blood flow is silent, while Turbulent blood flow creates sounds

What causes Turbulent Blood Flow?Case 1 • In a healthy person the

arteries are unobstructed• Blood is PUMPED from the

heart with a lot of force & it is PUSHED through the arteries at a high speed ( still below critical velocity)

• Blood flow is smooth (laminar and non-turbulent)

What causes Turbulent Blood Flow?

• Case 2• Patient now suffers from

atherosclerosis as a result of smoking• The lumen of his arteries have

become narrower due to a build up of plaque deposits.

• The same amount of blood as in case 1 is still PUMPED from the heart with a lot of force. However when that volume it is PUSHED through the arteries, there is less room for the blood to pass through.

• Consequently, in order to cope with the volume of blood being pumped (along with the force it is pumped with), the speed of the blood flow through the arteries increases.

• The speed of the person’s blood flow has now surpassed critical velocity

• The patient now has turbulent blood flow

What causes Turbulent Blood Flow?

• Turbulent blood flow results when the artery or heart valve is narrowed

Murmurs

• The main cause of murmurs is disease of the heart valves

Murmurs• Two main problems can occur with the heart valves

– Stenosis – The orifice of the heart valve is narrowed. Similar to the narrowed lumen of the patient with atherosclerosis blood flow through the valve in the normal direction is accelerated and turbulent

– Regurgitation or Insufficiency - the valve is incompetent. I.e. blood flows backwards through it, again through a narrow orifice which accelerates the flow.

Heart MurmursValve Abnormality Timing of

Murmur

Pulmonary or Aortic

Stenosis Systolic

Regurgitation Diastolic

Mitral or tricuspid

Stenosis Diastolic

Regurgitation Systolic

Detection

• Murmurs can usually be picked up during auscultation of the heart using a stethoscope.

• The “problem valve” can usually be identified by the location of the murmur– Aortic or pulmonary valves : heard at the base of

the heart– Mitral valve- heard best at the apex of the heart

Learning Objective 5

• Describe conduction of the cardiac impulse and the abnormalities of conduction.

Learning Objective 6

• List drugs that are used in the treatment of cardiac arrhythmias.

Medications a Doctor May Prescribe to Treat Cardiac Arrhythmias

• Heart medications have different effects on the body. Some medications act to slow the rate of the heart. These are called "rate control" medicines. Other medications act to help maintain a normal heart rhythm. These are called "rhythm control" medications or antiarrhythmic drugs.

Medications a Doctor May Prescribe to Treat Cardiac Arrhythmias

• Antiarrhythmic drugs are being used less, with more care and often in conjunction with implantable cardioverter defibrillators (ICDs) or cardiac ablation

• Many of the prescription medications reviewed here are also used to treat other kinds of heart-related conditions, including heart failure, high blood pressure, and angina (chest pain).

• The choice of medication used is based on the needs of the individual patient. The following are some of the medications used to treat arrhythmias and the differences between "rate" and "rhythm" control medicines.

Rate and Rhythm Medications

• Rate and rhythm medications are often a first course of action in managing atrial fibrillation.

• Rate control medications are used to slow the heart rate to less than 100 beats per minute. If rate control doesn't work, then a rhythm control medication may be used to try to restore your heart's normal sinus rhythm.

• Rhythm control medication is also called "drug cardioversion." If rate control medications are unsuccessful, then rhythm control medications are often used to restore the heart's normal sinus rhythm.

Rate Control Heart Medications

• Beta blockers:Beta-blockers slow heart rate, relax the blood vessels and make it easier for the heart to pump blood.

• Examples of Beta blockers:Acebutolol (Sectral®),Atenolol (Tenormin®),Carvedilol (Coreg®), Metoprolol (Toprol-XL®, Lopressor®),Sotalol (Betapace®)

Rate Control Heart Medications

• Calcium Channel Blockers:Calcium channel blockers are also called "calcium antagonists." These medicines work by interrupting the movement of calcium into heart and blood vessel tissue to slow heart rate.

• Examples of Calcium Channel Blockers:Diltiazem (Cardizem®, Tiazac®) and Verapamil (Calan®, Covera-HS®, Isoptin®)

Rhythm Control Heart Medications

• Sodium Channel Blockers:Sodium channel blockers slow the electrical conductivity of the heart to improve rhythm problems.

• Examples of Sodium Channel BlockersFlecainide (TambocorTM), Propafenone (Rythmol®) and Quinidine (Cardioquin®, Quinaglute Dura-Tabs®, Quinidex)

Anticoagulants

• Anticoagulant medications help to prevent new clots from forming in the blood or existing clots from getting larger. They are often prescribed for patients with atrial fibrillation to help reduce stroke risk.

• Aspirin also is often recommended for these patients in addition to or instead of prescription anticoagulants

Learning Objective 7

• Classify the drugs according to the Vaughn William Classification

Class Known as Examples Mechanism Clinical uses

1 sodium-channel blockade

Ia

fast-channel

blockers-Affect

QRS complex

Quinidine Procainamide Disopyramide

(Na+) channel block

(intermediate

association/dissoci

ation)

Ventricular arrhythmias prevention of paroxysmal 

recurrent atrial fibrillation (triggered by vagal overactivity)

procainamide in Wolff-Parkinson-White syndrome

IbDo not affect QRS

complex

Lidocaine Phenytoin Mexiletine Tocainide

(Na+) channel block

(fast

association/dissoci

ation)

treatment and prevention during and immediately aftermyocardial infarction, though this practice is now discouraged given the increased risk of asystole

ventricular tachycardia atrial fibrillation

Ic

Flecainide Propafenone Moricizine

(Na+) channel block

(slow

association/dissoci

ation)

prevents paroxysmal atrial fibrillation

treats recurrent tachyarrhythmias of abnormal conduction system.

contraindicated immediately post-myocardial infarction.

Class Known as Examples Mechanism Clinical uses

IIBeta-

blockers

Propranolol Esmolol Timolol Metoprolol Atenolol Bisoprolol

beta blocking

Propranolol also

shows some class I

action

decrease myocardial infarction mortality

prevent recurrence of tachyarrhythmias

III

Amiodarone Sotalol Ibutilide Dofetilide Dronedarone E-4031

K+ channel blocker

Sotalol is also a beta blocker[2] Amiodaronehas Class I, II, and III activity

In Wolff-Parkinson-White syndrome

(sotalol:) ventricular tachycardias and atrial fibrillation

(Ibutilide:) atrial flutter and atrial fibrillation

IV

slow-

channel

blockers

Verapamil Diltiazem

Ca2+ 

channel blocker

prevent recurrence of paroxysmal supraventricular tachycardia

reduce ventricular rate in patients with atrial fibrillation

V

Adenosine Digoxin Magnesium S

ulfate

Work by other or

unknown

mechanisms (Direct

nodal inhibition).

Used in supraventricular arrhythmias,

especially in Heart Failure with Atrial

Fibrillation, contraindicated in

ventricular arrhythmias. Or in the

case of Magnesium Sulfate, used in 

Torsades de Pointes.

Learning Objective 8

• Discuss the epidemiology and impact of congenital lesions of the cardiovascular system.

• (wasn’t feeling like doing the pub health)

Impact of congenital lesions of the cardiovascular system

• Congenital heart defects are structural problems with the heart present at birth. They result when a mishap occurs during heart development soon after conception and often before the mother is aware that she is pregnant.

• They may or may not have a disruptive effect on a person's circulatory system.

Impact of congenital lesions of the cardiovascular system

• Defects range in severity from simple problems, such as "holes" between chambers of the heart, to very severe malformations, such as complete absence of one or more chambers or valves.

Associated Conditions

• Having a congenital heart defect can increase your risk of developing certain medical conditions.– Pulmonary Hypertension– Arrhythmias– Infective Endocarditis– Anticoagulation– Congestive Heart Failure

Learning Objective 9

• Discuss the family’s response to ‘loss’ as in the situation of death. – the were sad and confused.

• They wanted answers as to why Joan died and if her death could have been prevented

Learning objective 10

• Discuss relevant issues in child health surveillance. – social workers etc should monitor and help at risk children keep up with their medical appointments